(1) Technical Field
This invention relates to a molded composite article and a process for producing the same, particularly to a molded composite article having a curved surface which is composed of at least one laminate comprising continuous filaments and a film and a process for producing the same.
(2) Background Information
With the recent development of sciences and industries, the situation is often brought about that the materials conventionally used in various fields are insufficient in their physical properties and can not perform the satisfactory functions. For example, with respect to the airplanes, the strength per weight and the modulus of the materials are required to be improved. In the field of space instruments, the development of the materials having the high specific strength and specific modulus is desired for a reduction of cost. Further, when the outside plates of the automotive vehicles are formed of plastic materials for decreasing their weight, the plastic materials having the high rigidity are required.
On the other hand, by the recent development of the textile techniques, the fibers having the strength per weight and the modulus higher than those of iron have been developed. For example, there are mentioned inorganic fibers such as carbon fibers, SiC fibers and boron fibers, and organic fibers such as p-aromatic polyamide fibers (for example, Kevlar.RTM. supplied by Du Pont and Technora.RTM. supplied by Teijin Limited) and high density polyethylene fibers (for example, Techmilon.RTM. supplied by Mitsui Petrochemical Industries, Ltd.). It is thought that these high performance fibers are bound with a resin to provide a new material or incorporated in the conventional resin, metal or the like for reinforcement. These processes have partially been employed for practical use. For example, there are mentioned a FRP (Fiber Reinforced Plastic), a FRM (Fiber Reinforced Metal), a CC (Carbon-Carbon) composite and the like.
Theoretically, the continuous filaments are superior to the staple fibers in reinforcing effect of the composite material. Therefore, in case that the FRP product is produced by using the most advanced composite, the continuous filaments are combined with the thermosetting resin of B stage. When the FRP product is manufactured by using the thermoplastic resin, the staple fibers are generally employed as reinforcing fibers. In this case, however, the product are limited in physical properties. Further, the staple fibers come to appear at the surface of the product and the surface is roughened, whereby the appearance of the product is deteriorated. On the other hand, when the thermosetting resin of B stage is used, there are the problems that the resin is inferior in processability including storage stability because of a considerable change with the passage of time, and that the resin is required to be cured by heat treatment. Therefore, the composite materials prepared by the combination of the continuous filaments and the thermoplastic resins have recently been studied.
However, these composite materials have a problem that they are inferior in handling easiness because of their hardness. For solving this problem, it has been considered that the fabric composed of the same thermoplastic resin as the matrix resin to be melted is combined therewith td provide the composite material. It has also been studied that the fabric for reinforcement and the film of the matrix resin, each of which is separately prepared, are alternately laminated when molded and then the film is melted. The composite material obtained according to these processes is restricted by the shape of the molded article, because the fabric lacks in stretchability when laminated and molded. That is to say, it is difficult to form the composite material into a curved surface, particularly into a spherical surface. Further, the adhesion of the fibers with the matrix resin is not necessarily good. Furthermore, as the important fact, when the composite material reinforced with the continuous filament fabric is formed into a curved surface, the continuous filament fabric is broken on molding. Accordingly, the reinforcing effect is often reduced to the degree similar to that of the staple fiber fabric. In some cases, the composite material itself comes to be broken.
Further, even if the continuous filaments unidirectionally paralleled are used for reinforcement, when the sufficient tension is not applied to the filaments on molding, the tensile strength or the initial modulus of the molded article is liable to vary or not to be satisfactorily increased. Thus the satisfactory results can not be obtained.
On the other hand, Japanese Patent Application Laid-open No. 28683/1978 discloses a decorative laminated sheet wherein a transparent film having a back-printed moire pattern is laminated on a substrate sheet comprising fibers or filaments unidirectionally paralleled and fixed. Japanese Utility Model Application Laid-open No. 85825/1980 further discloses a heat-resistant composite material comprising a continuous filament sheet unidirectionally arranged and a heat-resistant film laminated therewith. However, the former is used as a decorative sheet for a building material, particularly as a film-form pattern paper, and the latter is used as an electrical insulating tape. These are different from the molded composite article having a curved surface claimed in the present invention.
U.S. Pat. Nos. 3,664,909, 3,713,962 and 3,850,723 further disclose a composite mat structure for use in reinforced stampable resinous articles comprising a mat of fibrous strands and a mat of unstranded filaments, the mats being impregnated with a resin, and the preparation thereof. This composite material is more easily formed into a curved surface, particularly into a spherical surface than the composite material reinforced with the fabric described above. However, the molded article prepared from this material is inferior in physical properties and the surface thereof is liable to be roughened.